Hi,
Yes, we clear the PYTHONPATH argument as this often causes conflicts between the Cylc/Rose environment and the job environment (context).
If you need to add a module into the Cylc/Rose environment’s Python path (and not the job environment’s Python path), use the CYLC_PYTHONPATH and ROSE_PYTHONPATH variables.
However, this isn’t necessary for normal installations, it’s only required if things have been installed into non-standard locations so PYTHONPATH is needed to locate them.